As small portable electronic devices become increasingly integrated into users' lives, the frequency of interaction between users and devices has increased greatly. Fortunately, non-textual entry mechanisms have developed to facilitate more seamless and simple user interaction. One of the primary non-textual entry mechanisms is gesture recognition, wherein ideally a device detects a gesture made by the user, e.g., with the user's hands, translates the detected gesture into a desired action, and executes the desired action. For example, a user may make a gesture that corresponds to a command to open the camera app on the device. If the device correctly detects and interprets this gesture, then it will open the camera app without requiring any physical interaction from the user.
However, the usability of such systems depends almost entirely upon the device's ability to correctly detect gestures. Typically, thermal sensors are used for presence detection and hand gesture detection. Such sensors work by measuring a temperature difference between the room or ambient temperature and the user's presumably higher hand temperature. This measurement is a delta measurement that depends upon a difference in temperature, but the measured difference will change with any changes in the user's hand temperature or in the ambient temperature.
In addition, the distance between the sensor and the user's hand also affects the temperature measurement. This is because the thermal sensor takes a measurement in its field of view (FOV). So for example, a close hand takes up a greater portion of the sensor's FOV than the same hand further away. This of course leads to a higher FOV temperature the closer the hand is to the sensor, regardless of the hand's actual temperature.
As a corollary example, a hot hand in a cold room will be accurately detected at a farther distance than a warm hand in the same room. Thus, the range of operation of a gesture detection system may differ among different users in the same room and may even differ for the same user when in different rooms.
Before proceeding to the remainder of this disclosure, it should be appreciated that the disclosure may address some or all of the shortcomings listed or implicit in this Background section. However, any such benefit is not a limitation on the scope of the disclosed principles, or of the attached claims, except to the extent expressly noted in the claims.
Additionally, the discussion of technology in this Background section is reflective of the inventors' own observations, considerations, and thoughts, and is in no way intended to be, to accurately catalog, or to comprehensively summarize any prior art reference or practice. As such, the inventors expressly disclaim this section as admitted or assumed prior art. Moreover, the identification or implication herein of one or more desirable courses of action reflects the inventors' own observations and ideas, and should not be assumed to indicate an art-recognized desirability.